1. Field of the Invention
The present invention is in the field of mechanical locking devices and specifically relates to a device of the type in which the locking is effected by a coiled spring which grips a rod, for clamping two members against translational motion and for selectively enabling such motion when the ends of the springs are twisted in opposite directions simultaneously to unwind the coiled springs, thereby relaxing its grip on the rod.
2. The Prior Art
The present invention includes a rod which extends into a cylindrical housing. Normally, the present invention locks the rod with respect to the housing so that axial translational motion of the rod relative to the housing is prevented. The mechanical lock can be selectively actuated to an unlocked state in which motion of the rod is enabled. In the present invention, the opposite ends of the spring are each connected to actuator levers which are used to rotate the opposite ends of the spring in opposite directions to unwind the spring, so that its diameter increases slightly, thereby causing the spring to relax its grip on the rod, which may then be moved freely axially relative to the housing.
The use of a coiled spring to grip a rod extending coaxially through the spring is well known. A number of locking devices making use of this basic principle have been patented. While all of the patented devices use this same fundamental principle, the implementations employed are patentably distinct. The present invention is believed to provide still another new and useful implementation.
In U.S. Pat. No. 3,230,595 issued Jan. 25, 1966 to Kedam, there is shown a rod-clamping device in which both ends of the spring are rotated simultaneously to lock and unlock the device. However, rotation of the ends of the spring is not produced by an actuator lever, but instead by grooves which exert a camming action on the ends of the spring. The device described in Kedam's patent includes no provision for causing the last few turns at each end of the spring to become cocked on the rod to produce a more positive locking engagement.
This latter feature is shown clearly in U.S. Pat. No. 3,249,180 issued May 3, 1966 to Torossian and in U.S. Pat. No. 2,750,994 issued June 19, 1956 to Howell. However, in these patents, only one end of the spring is rotated to lock and unlock the device and therefore the stroke required is longer than in the present invention.
In U.S. Pat. No. 3,874,480 issued Apr. 1, 1975 to Porter et al., there is described a friction brake mechanism in which two springs are unwound simultaneously to unlock the grip of the springs on a rod. Also, in U.S. Pat. No. 3,064,766 issued Nov. 20, 1962, Hanizeski shows a spring lock in which two separate springs are simultaneously unwound by an electromagnetic device to produce the desired unlocking.
All of the above-mentioned inventions can be distinguished on the basis of their structures from the device of the present invention. The present invention arose from the desirability of having a true locking action of the type wherein the last few turns at the ends of the spring become cocked on the rod, but at the same time being releasable by actuation through a relatively short stroke and by means of a cable which extends in the axial direction. This particular combination of features was unavailable in the known prior art and necessitated the present invention.